1. Field of the Invention
The present invention relates to a thin film magnetic head employing a magnetoresistance effect device (hereinafter, referred to as an MR device). In particular, the present invention relates to a thin film magnetic head for significantly high density magnetic recording having a remarkably narrow shield gap length.
2. Description of the Related Art
A thin film magnetic head employing an MR device have long been under development. FIG. 6 shows a cross-sectional view of a thin film magnetic head having a conventional MR device.
The conventional thin film magnetic head 200 includes a recording head section 180 and a reproducing head section 190. The recording head section 180 includes head cores 12 and 13 formed of magnetic substance, and a recording gap 14 formed of a non-magnetic insulating film. In addition, a winding conductor 11 is provided through the non-magnetic insulating film. In the recording head section 180, a magnetic field generated by current flowing through the winding conductor 11 is converged to the head cores 12 and 13, and thus recording to a medium is performed by the magnetic field leaked from the recording gap 14. This type of recording head section 180 is referred to as an inductive type recording head.
On the other hand, the reproducing head section 190 includes an upper shield 13 (functioning as the recording head core 13) and a lower shield 16 formed of magnetic films, and an MR device section 15 in a shield gap 17 between the upper and lower shields 13 and 16. The MR device section 15 is insulated from the upper shield 13 and the lower shield 16 by insulating films 18. A lead section 19 is formed so as to supply current in a direction of the plane of the thin film MR device section 15. Conventionally, as a material for the MR device section 15, a permalloy (e.g., Ni.sub.0.6 Fc.sub.0.2) is used. The reproducing head section 190, which is a magnetoresistance effect type head, detects a change in a signal magnetic field from a medium as a change in the electric resistance of the MR device section 15, and this makes it possible for the head section 190 to read out a signal recorded in the medium.
However, the following problems arise in achieving high density recording when the conventional technique described above is used. Since a shield gap length (denoted by d.sub.eg in FIG. 6) is required to be equal to or shorter than the shortest signal wavelength to be reproduced, it is necessary to further reduce the thicknesses of the insulating films 18 and the MR device section 15 with further development of high density recording. In the future, the shield gap length is expected to be about 100 nm or less, and there will be a need for the thickness of the insulating film 18 to be about 50 nm or less. However, to the detriment of achieving high density recording, it is technically difficult to form an insulating film having a thickness of about 50 nm or less and maintain good insulating properties.